Index templates allow you to define templates that will automatically be applied when new indices are created. The templates include both settings and mappings, and a simple pattern template that controls whether the template should be applied to the new index.

Templates are only applied at index creation time. Changing a template will have no impact on existing indices.

For example:

PUT /_template/template_1
{
  "template": "te*",
  "settings": {
    "number_of_shards": 1
  },
  "mappings": {
    "type1": {
      "_source": {
        "enabled": false
      },
      "properties": {
        "host_name": {
          "type": "string",
          "index": "not_analyzed"
        },
        "created_at": {
          "type": "date",
          "format": "EEE MMM dd HH:mm:ss Z YYYY"
        }
      }
    }
  }
}

Defines a template named template_1, with a template pattern of te*. The settings and mappings will be applied to any index name that matches the te* template.

It is also possible to include aliases in an index template as follows:

curl -XPUT localhost:9200/_template/template_1 -d '
{
    "template" : "te*",
    "settings" : {
        "number_of_shards" : 1
    },
    "aliases" : {
        "alias1" : {},
        "alias2" : {
            "filter" : {
                "term" : {"user" : "kimchy" }
            },
            "routing" : "kimchy"
        },
        "{index}-alias" : {} 
    }
}
'

Deleting a Templateedit

Index templates are identified by a name (in the above case template_1) and can be deleted as well:

curl -XDELETE localhost:9200/_template/template_1

Getting templatesedit

Index templates are identified by a name (in the above case template_1) and can be retrieved using the following:

curl -XGET localhost:9200/_template/template_1

You can also match several templates by using wildcards like:

curl -XGET localhost:9200/_template/temp*
curl -XGET localhost:9200/_template/template_1,template_2

To get list of all index templates you can run:

curl -XGET localhost:9200/_template/

Templates existsedit

Used to check if the template exists or not. For example:

curl -XHEAD -i localhost:9200/_template/template_1

The HTTP status code indicates if the template with the given name exists or not. A status code 200 means it exists, a 404 it does not.

Multiple Template Matchingedit

Multiple index templates can potentially match an index, in this case, both the settings and mappings are merged into the final configuration of the index. The order of the merging can be controlled using the order parameter, with lower order being applied first, and higher orders overriding them. For example:

curl -XPUT localhost:9200/_template/template_1 -d '
{
    "template" : "*",
    "order" : 0,
    "settings" : {
        "number_of_shards" : 1
    },
    "mappings" : {
        "type1" : {
            "_source" : { "enabled" : false }
        }
    }
}
'

curl -XPUT localhost:9200/_template/template_2 -d '
{
    "template" : "te*",
    "order" : 1,
    "settings" : {
        "number_of_shards" : 1
    },
    "mappings" : {
        "type1" : {
            "_source" : { "enabled" : true }
        }
    }
}
'

The above will disable storing the _source on all type1 types, but for indices of that start with te*, source will still be enabled. Note, for mappings, the merging is "deep", meaning that specific object/property based mappings can easily be added/overridden on higher order templates, with lower order templates providing the basis.